First stomach 

 (rumen) 



Connection 

 of gullet 



Fourth 



stomach 



(abomasum) 



Connection 

 of intestine 



Gullet 



Second stomach 

 (reticulum) 



Third stomach 

 (omasum) 



THE STOMACHS OF A CUD-CHEWING ANIMAL 



The cow swallows food into the first stomach without chewing it. The contents of the 

 stomach are returned to the mouth in small quantities when the animal is lying quietly, 

 and thoroughly chewed. The mixture of saliva and ground food is then swallowed 

 into the second and third pouches of the stomach, where salivary digestion continues. 

 In the fourth stomach gastric digestion of protein goes on 



some comfortable spot, regurgitate a wad at a time and grind it to bits 

 When the cud is thoroughly macerated, it is swallowed mto the second 

 stomach, and on it goes through the remainder of the food tube. Bacteria 

 in the food tube decompose the cellulose of the plant tissues, exposmg the 

 cell contents of the swallowed material to the digestive juices. 



Off the Main Line In many animals, the horse, rabbit and rat, for 

 example, food in the digestive tube is held up for a considerable time in a 

 blind gut. This side branch of the large intestine is located at the junction 

 of the small and large intestines, and is called the caecum, from a Latin 

 word meaning "blind". Chickens and doves have two caeca. Bacteria in 

 the caecum digest the cellulose of plant tissues, as they do in the first 

 stomach of ruminating animals. At the end of the caecum, in most mam- 

 mals, is an extension or appendix. In some species this is "wormlike' and 

 hence is called the "vermiform" appendix (see illustration opposite). In 

 many the blind gut is small and has a poor blood supply. An infection of 

 the appendix, a condition known as "appendicitis", is often serious. 



174 



